Green Degumming Processes of Silk: Comparison
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Please note this is a comparison between Version 2 by Dean Liu and Version 1 by Lei Zhu.

Traditional textile degumming processes, including soap, alkali or both, could bring such problems as environmental damage, heavy use of water and energy, and damage to silk fibroin. The residual sericin may influence the molecular weight, structure, morphology and properties of silk fibroin, so that degumming of silk is important and necessary, not only in textile field but also in non-textile applications.

  • silk filaments
  • fibroin
  • sericin
  • green degumming
  • enzyme

1. Introduction

Silk, generally known as the “queen of fiber”, has not only been used in the textile field but also in biomedical field [1,2,3][1][2][3]. In fact, silk can be produced by the species from Arachnida or Lepidoptera, such as mites, butterflies and moths [4]. Among such kinds of silks, those from the domesticated silkworms (Bombyx mori) are used mostly. Unless otherwise stated, silk in this paper points to the Bombyx mori silk.
The silk is mainly composed of two kinds of proteins, the inner insoluble fibrous protein, which is usually named fibroin, and the outer global hydrophilic protein, named sericin [2,5][2][5]. Due to big differences, such as appearance, solubility, amino acid composition and amount of reactive groups, silk fibroin and sericin usually needs to be separated before further processing.
In textile fields, in order to obtain silk fibroin filaments with an excellent hand, elegant luster, high capillary rise height, a process called degumming (also called scouring) is necessary [6,7][6][7]. Sometimes, when the whiteness of silk fibroin filaments is not good enough, bleaching is applied [6]. After degumming, silk fibroin filaments can be dyed, printed or finished for textile applications. While in non-textile field, purified silk fibroin can be obtained through a simple degumming process, such as alkali degumming and boiling water. After that, silk fibroin can be further processed to film, sponge, scaffold, hydrogel, and non-woven mats for non-textile applications.

2. Types of  Green Degumming

Traditional degumming processes could cause problems such as environmental damage, heavy use of water and energy, and damage to silk fibroin. 

2.1. Enzyme Degumming

Enzymes, usually composed of amino acids, are one kind of large biological molecules biocatalyst, which can be widely used in textile field, such as pretreatment of cotton, degumming of silk, bleaching and shrink proofing of wool due to their mild conditions of temperature and pH, high specificity and efficiency, reduced water and energy consumption [8,9][8][9] and little damage to silk fibroin [10,11,12,13][10][11][12][13]. It is reported that more than three quarters of industrial enzymes are hydrolytic in action, while protein-degrading enzymes count for two over five [8]. Among protein-degrading enzymes, proteases are the largest group with animal, plant and microbial sources which could be active under alkaline, acidic and neutral conditions [9].
In order to completely separate sericin from silk fibroin without obvious hydrolytic damage to the latter, Li et al. [11] used papain to degum Bombyx mori silk filaments under nearly neutral conditions. They found that sericin was completely removed, and silk fibroin still had a high molecular weight when the concentration of papain reached 3.0 g/L. This could be explained because, here, papain specifically breaks the binding sites between L-arginine or L-lysine residue and another amino acid residue in sericin, resulting in the clean and smooth surface of silk fibroin. Furthermore, they also found higher tensile strength using papain degumming than that under the traditional degumming process with sodium carbonate. They further prove that papain is a good alternative for degumming silk.
Besides, Promboon et al. [14] selected a commercial grade stem bromelain as the effective degumming agent for Mai 1 silk filaments. The results indicated that the fibroin was not damaged, and the silk fabric was provided with good physical properties, such as tensile strength with bromelain degumming method, compared with traditional sodium carbonate degumming method. Although bromelain is shown as a good biocatalyst, active pH range and corresponding mechanism of action were not reported.
Freddi et al. [15] picked up four such commercial proteases for silk degumming process including oxidative-stable endopeptidase, bacterial high alkaline strain, papain and aspergillus pepsin I. They found that only alkaline and neutral proteases were effective for the degumming of silk filaments, while the acid protease was ineffective under the experimental conditions adopted. Further study showed that even though the degumming ratio reached 25%, there was almost no sericin remaining on the warp of silk filaments while still some sericin deposited on the highly twisted weft, indicating that texture of silk could also influence the effect of degumming.
Recently, Chim-anage et al. [16] screened and isolated an extracellular serine protease of Bacillus sp. C4 SS-2013 (C4), used for the degumming of silk filaments. They found that the protease has a high specificity to sericin protein, and even at incubation for three days, the silk fibroin was not damaged while the sericin was completely removed. Furthermore, this protease was easily concentrated and suitable for longer storage at low temperatures. Although C4 is a promising alternative for degumming silk, whether it can be in large-scale production and for wide applications is still unknown.
Apart from the above teams devoted to studying the biological degumming of silk filaments with enzymes, other groups also promote this art [17,18,19,20,21,22,23,24,25,26,27][17][18][19][20][21][22][23][24][25][26][27]. It is anticipated that with the discovery, screen and isolation of more enzymes suitable for the silk degumming, corresponding environmentally friendly and green degumming processes will be developed and make silk degumming flourish.

2.2. CSCF Degumming

CO2 supercritical fluid (CSCF) can be considered as the CO2 above its critical temperature (Tc, generally 304.25 K) and critical pressure (Pc, generally 7.38 MPa), under which CO2 shows some unique properties, such as appropriate viscosity and diffusivity like gas, appropriate density and solvating properties like liquid, making it as solvent candidate so that CSCF can be applied in many fields [28,29,30,31,32,33,34,35,36,37][28][29][30][31][32][33][34][35][36][37]. In textile fields, CSCF is usually used for dyeing due to its environmentally friendly nature for the replacement of organic solvents or water and easy recovery and recycling [28[28][29][30],29,30], compared with traditional dyeing process. Besides the application in dyeing synthetic or natural fibers, CSCF can also be used for pretreatment of cotton [34,35][34][35] and flax fibers [36,37][36][37]. However, up to now, little information on degumming of silk using CSCF was reported.
Lo and his collaborator [32,33][32][33] conducted a series of studies on silk degumming using CSCF. The whole process includes the acid pretreatment of silk filaments with the aid of a surfactant, treatment with CSCF in the container under appropriate conditions and post-treatment using ultrasonic method. In this way, the cleaned silk fibroin filaments could be obtained. The mechanism could be explained that after pretreatment with citric acid or tartaric acid, the silk filaments carry positive charges due to both the isoelectric point (pI) of silk fibroin (3.6) and sericin (3.3) higher than experiment pH (2–3) [31,32,33][31][32][33]. Since citric acid or tartaric acid contains a carboxylic acid group, they can interact with the hydrogen ion (proton) on the surface of silk sericin to damage the amino acid structure of the sericin and with the help of a surfactant, a hydrophilic site will be created under CSCF. Then sericin can be easily removed from silk filaments by ultrasonic post-treatment. Although silk degumming using CSCF is efficient and can keep silk fibroin less damaged than conventional ammonium hydroxide degumming method, the complicated process is required. Hence, the development of easy and efficient degumming process of silk filaments with less damage to silk fibroin by CSCF method is quite necessary.

2.3. Acid Degumming

Besides enzymes and CSCF degumming, degumming of silk filaments with citric acid can also be considered an environmentally friendly degumming process due to the biodegradable nature, reduced water consumption and less damage to silk fibroin [38,39][38][39]. Citric acid (CA) is a mild organic acid with good biodegradability, safe and pleasant taste, high water solubility, good chelating and buffering properties which has been widely used in food, cosmetic, chemical and biomaterials fields [38,39,40,41][38][39][40][41].
In biomaterials field, citric acid acts as a green cross-linker for various applications, such as tissue engineering, cancer therapy, wound dressings [42,43][42][43]. It is interesting to point out that, in textile field, citric acid was first used as the cross-linker for the textile finishing instead of pretreatment [44,45,46,47][44][45][46][47].
Tsukada et al. [48] applied different concentration of citric acid for the degumming of silk filaments to study the effect of citric acid treatment on structure, morphology and properties of silk filaments. They found that molecular conformation and the crystalline structure did not change after degumming with citric acid, and almost no sericin remained on the surface of silk filaments with 30% citric acid when the total weight loss reached 25.4%, together with good tensile properties. They stated that citric acid degumming can be an alternative for industrial application. However, the pH of degumming bath containing 30% citric acid was not reported and whether such conditions can be suitable for industrial applications is still unknown.

2.4. Steaming Degumming

As one kind of efficient processing methods for the biomass conversion, the used steam has higher efficiency of heat transfer due to its greater heat capacity and not decreasing the moisture content of treated objects like wood, compared with hot air [49,50,51][49][50][51]. In the textile wet process, steam treatment is often used for padding dyeing, printing and finishing process [52,53,54,55,56][52][53][54][55][56].
Similar to CSCF degumming, the steam process for textiles seems to be the environmentally friendly due to no harmful chemicals use and low water consumption. However, litter information on steaming process for pretreatment of silk filaments. Recently, Zhu et al. [57] showed a routine of silk degumming by steam treatment without aid of any chemicals. They used a modified pressure cooker as the steam treatment apparatus. Ultrasonic treatment and following washing process was applied after the steam degumming. The results show that sericin was almost completely removed under optimal conditions, and some physicochemical properties of the silk fibroin filaments did not change. Energy efficiency analysis indicates steam treatment is an efficient technique for raw silk degumming with lower processing cost and without chemical used, compared to the conventional chemical degumming methods. Since steam degumming for raw silk filaments can be considered as an environmentally friendly and green process, large scale of steam degumming of silk filaments for textile applications and non-textile applications is worthy of further investigation.

2.5. Ultrasonic Degumming

In biomedical applications, sonication becomes a useful tool to control the rapid sol-gel transition of silk fibroin to form hydrogel, and to regulate the protein structure to obtain protein-base materials [58,59,60][58][59][60]. In textile field, ultrasonication is also widely used for dye extraction, textile dyeing due to the ability of sonication of breaking aggregates of dyes, breaking the fiber-dye interfacial layer and increasing the swelling of fiber to accelerate their diffusion into the fiber [61,62,63][61][62][63].
Besides, sonication is also often seen in textile washing, including pretreatment and post-treatment [57,64,65,66][57][64][65][66]. With this technique, fewer chemicals are used and washing effectiveness is improved [64[64][65][66],65,66], therefore, ultrasonication can be thought to be an environmentally friendly and green process.
However, up to now, there is less information on degumming of silk filaments with sonication [67,68][67][68]. Recently, Arami et al. [67] applied different degumming techniques based on ultrasonication for raw silk yarns. In short, such techniques can be divided into two groups: one-bath degumming process and two-bath process, and the former group includes ultrasound degumming, ultrasound–enzyme degumming and traditional soap-alkali degumming, while the latter includes ultrasound and soap degumming, ultrasound and enzyme degumming, ultrasound and enzymes mixture degumming. The results show that the optimal degumming process is two-bath based ultrasound and enzymes mixture degumming, with significantly increased degumming efficiency perhaps due to their synergetic effect. Such a sonication-based environmentally friendly degumming process is very meaningful and important because it can help other research teams try different combinations of degumming process, develop many eco-friendly degumming processes and achieve a wide range of applications. Similar to the work by Arami, Li et al. [68] applied the citric acid, sodium carbonate and papain as the degumming agents for the silk filaments reeled from silk cocoons with the aid of ultrasonic treatment at four different frequencies. They found that a higher degumming rate was obtained degummed by ultrasonication at a lower frequency than at a higher frequency. They also found that papain degumming was more effective than citric acid and sodium carbonate with higher degumming rate. With increasing degumming temperature and time, less sericin was remained on the surface of silk filaments with papain degumming, resulting in smooth and clean surface, however, this may decrease silk whiteness. Sonication-based environmentally friendly degumming process is very meaningful and important because it can help other research teams try different combinations of degumming process, develop many eco-friendly degumming processes and achieve a wide range of applications.
In order to make cost and technical comparison with conventional degumming process, advantages and limitations of art of environment-friendly silk degumming are listed in Table 1. Although conventional soap, alkali or soap-alkali degumming displays their advantages of simple process and wide application, chemicals cannot be recycled, silk fibroin may be damaged, and demand of water and energy is high. For comparison, art of enzyme, CO2 supercritical fluid, acid, steam and ultrasonic degumming shows different advantages and limitations.
Table 1.
 Comparison of art of environment-friendly silk degumming with the conventional.
Art Advantages Limitations References
Enzyme Mild conditions Relatively high cost [11,12,13,14,15,16,17,18,19,,22,23,24,25,26,27][11][12]20,[13][14][15][16][17][18][19][20]21[21][22][23][24][25][26][27]
More choice of enzymes Easy deactivation
Little damage to fibroin

High specificity and efficiency
CO2 supercritical fluid Recycling of CO2 High requirements for equipment [32,33][32][33]
Little damage to fibroin Demand of acid pretreatment and ultrasonic post-treatment
Acid Smooth and clean surface Slightly decreased dye uptake percentage [48,68][48][68]
Increased tensile strength
Steam Relative lower cost Lack of industrial application [57]
No addition of chemicals
Ultrasonic Improved degumming efficiency Demand of addition of soap, alkali, acid or enzyme [38,67,][38][67]68[68]
Reduced use of water and chemical Low conversion of electrical to acoustical energy
Conventional soap, alkali or soap-alkali Simple process

Wide application		 Unrecyclable chemicals [38,57,67,68][38][57][67][68]
Damage to fibroin

High demand of water and energy
Besides the previously mentioned green degumming processes, ozone degumming [69[69][70][71][72],70,71,72], microwave irradiation degumming [31[31][73],73], green nonionic surfactant degumming [74] can also be considered as green degumming process. On the other hand, traditional alkali degumming with Na2CO3 is not considered as green degumming process, however, Bucciarelli et al. [75] optimized the alkali degumming process with Na2CO3 by design of experiment (DOE) and successfully removed all sericin from the silk fibroin with less salt, water, and energy, compared with traditional alkali degumming method, stating that it is possible to make this technique overall more environmentally sustainable. Therefore, traditional degumming process may be developed to become environmentally friendly technique by well-designed experiments.

References

  1. Konwarh, R. Can the venerated silk be the next-generation nanobiomaterial for biomedical-device designing, regenerative medicine and drug delivery? Prospects and hitches. Bio-Des. Manuf. 2019, 2, 278–286.
  2. Vepari, C.; Kaplan, D.L. Silk as a biomaterial. Prog. Polym. Sci. 2007, 32, 991–1007.
  3. Kundu, B.; Kurland, N.E.; Bano, S.; Patra, C.; Engel, F.B.; Yadavalli, V.K.; Kundu, S.C. Silk proteins for biomedical applications: Bioengineering perspectives. Prog. Polym. Sci. 2014, 39, 251–267.
  4. Kaplan, D.L.; Mello, S.M.; Arcidiacono, S.; Fossey, S.; Senecal, K.W.M. Protein Based Materials; Birkhauser: Boston, MA, USA, 1998.
  5. Zhou, C.Z.; Confalonieri, F.; Medina, N.; Zivanovic, Y.; Esnault, C.; Yang, T.; Jacquet, M.; Janin, J.; Duguet, M.; Perasso, R.; et al. Fine organization of Bombyx mori fibroin heavy chain gene. Nucleic Acids Res. 2000, 28, 2413–2419.
  6. Wang, J.; Sun, K. Principle of Dyeing and Finishing; China Textile Industry Press: Beijing, China, 1984.
  7. Long, J.J.; Wang, H.W.; Lu, T.Q.; Tang, R.C.; Zhu, Y.W. Application of Low-Pressure Plasma Pretreatment in Silk Fabric Degumming Process. Plasma Chem. Plasma Process. 2008, 28, 701–713.
  8. Choudhury, A.R. Sustainable Textile Wet Processing: Applications of Enzymes, Roadmap to Sustainable Textiles and Clothing; Springer: Berlin/Heidelberg, Germany, 2014; pp. 203–238.
  9. Naveed, M.; Nadeem, F.; Mehmood, T.; Bilal, M.; Anwar, Z.; Amjad, F. Protease—A Versatile and Ecofriendly Biocatalyst with Multi-Industrial Applications: An Updated Review. Catal. Lett. 2021, 151, 307–323.
  10. Thakur, N.; Goyal, M.; Sharma, S.; Kumar, D. Proteases: Industrial applications and approaches used in strain improvement. Biol. Forum—Int. J. 2018, 10, 158–167.
  11. Feng, Y.; Lin, J.; Niu, L.; Wang, Y.; Cheng, Z.; Sun, X.; Li, M. High Molecular Weight Silk Fibroin Prepared by Papain Degumming. Polymers 2020, 12, 2105.
  12. Araujo, R.; Casal, M.; Cavaco-Paulo, A. Application of enzymes for textile fibres processing. Biocatal. Biotransform. 2008, 26, 332–349.
  13. Kim, J.; Kwon, M.; Kim, S. Biological Degumming of Silk Fabrics with Proteolytic Enzymes. J. Nat. Fibers 2016, 13, 629–639.
  14. Ninpetch, U.; Tsukada, M.; Promboon, A. Mechanical Properties of Silk Fabric Degummed with Bromelain. J. Eng. Fibers Fabr. 2015, 10, 69–78.
  15. Freddi, G.; Mossotti, R.; Innocenti, R. Degumming of silk fabric with several proteases. J. Biotechnol. 2003, 106, 101–112.
  16. Suwannaphan, S.; Fufeungsombut, E.; Promboon, A.; Chim-Anage, P. A serine protease from newly isolated Bacillus sp. for efficient silk degumming, sericin degrading and colour bleaching activities. Int. Biodeterior. Biodegrad. 2017, 117, 141–149.
  17. Toprak, T.; Anis, P.; Akgun, M. Effects of environmentally friendly degumming methods on some surface properties, physical performances and dyeing behaviour of silk fabrics. Ind. Textila 2020, 71, 380–387.
  18. Anis, P.; Toprak, T.; Yener, E.; Capar, G. Investigation of the effects of environmentally friendly degumming methods on silk dyeing performance. Text. Res. J. 2019, 89, 1286–1296.
  19. Chen, J.H.; Chen, X.; Zhang, X.Y.; Lan, G.Q. Process technology for using papain protease in fresh cocoon degumming and reeling. Sci. Sericult. 2016, 42, 111–117.
  20. Wu, C.; Wang, J.; Li, X.; Yu, Z. Research on scouring process of silk fabric with papain Q. Adv. Text. Technol. 2017, 25, 43–46.
  21. Gulrajani, M.; Agarwal, R.; Chand, S. Degumming of silk with a fungal protease. Indian J. Fibre Text. 2000, 25, 138–142.
  22. Vyas, S.K.; Shukla, S.R. Comparative study of degumming of silk varieties by different techniques. J. Text. Inst. 2015, 107, 191–199.
  23. Krishnaveni, V. Study on effect of proteolytic enzyme degumming on dyeing of silk. Colourage 2010, 57, 61–68.
  24. Nakpathom, M.; Somboon, B.; Narumol, N. Papain enzymatic degumming of Thai Bombyx mori silk fibers. J. Microsc. Soc. Thail. 2009, 23, 142–146.
  25. Ibrahim, N.; El Hossamy, M.; Nessim, A.; Hassan, T. Performance of bio-degumming versus conventional degumming processes. Colourage 2007, 54, 63–74.
  26. Gowda, K.; Padaki, N.V.; Sudhakar, R.; Subramani, R. Eco-friendly preparatory process for silk: Degumming by protease enzyme. Man-Made Text. India 2007, 50, 28–31.
  27. Gulrajani, M.; Gupta, S.V.; Gupta, A.; Suri, M. Degumming of silk with different protease enzymes. Indian J. Fibre Text. 1996, 21, 270–275.
  28. Banchero, M. Recent advances in supercritical fluid dyeing. Color. Technol. 2020, 136, 317–335.
  29. AbouElmaaty, T.; Abd El-Aziz, E. Supercritical carbon dioxide as a green media in textile dyeing: A review. Text. Res. J. 2018, 88, 1184–1212.
  30. Knez, Z.; Markocic, E.; Leitgeb, M.; Primozic, M.; Hrncic, M.K.; Skerget, M. Industrial applications of supercritical fluids: A review. Energy 2014, 77, 235–243.
  31. Rastogi, S.; Kandasubramanian, B. Processing trends of silk fibers: Silk degumming, regeneration and physical functionalization. J. Text. Inst. 2020, 111, 1794–1810.
  32. Lo, C.H. Degumming silk by CO2 supercritical fluid and their dyeing ability with plant indigo. Int. J. Cloth. Sci. Technol. 2021, 33, 465–476.
  33. Lo, C.H.; Chao, Y. Degumming of silk fibers by CO2 supercritical fluid. J. Mater. Sci. Chem. Eng. 2017, 5, 1–8.
  34. Liu, S.Q.; Chen, Z.Y.; Sun, J.P.; Long, J.J. Ecofriendly pretreatment of grey cotton fabric with enzymes in supercritical carbon dioxide fluid. J. Clean. Prod. 2016, 120, 85–94.
  35. Shi, W.; Liu, S.Q.; Sun, J.P.; Long, J.J. A strategy for environmentally-friendly removal of impurities from cotton based on biocatalytic reaction in supercritical carbon dioxide. Cellulose 2018, 25, 6771–6792.
  36. Zhang, J.; Zheng, H.D.; Zheng, L.J. Effect of treatment temperature on structures and properties of flax rove in supercritical carbon dioxide. Text. Res. J. 2018, 88, 155–166.
  37. Zhang, J.; Zheng, H.D.; Zheng, L.J. A Novel Eco-Friendly Scouring and Bleaching Technique of Flax Rove Using Supercritical Carbon Dioxide Fluid. J. Eng. Fibers Fabr. 2017, 12, 44–51.
  38. DeBari, M.K.; King, C.I.; Altgold, T.A.; Abbott, R.D. Silk Fibroin as a Green Material. ACS Biomater. Sci. Eng. 2021, 7, 3530–3544.
  39. Sharma, A.; Kumar, A.; Kapoor, A.; Kumar, R.; Gangal, S.V.; Gangal, V.; Makhijani, S.D. Assessment of biodegradability of organic acids by a defined microbial mixture. Bull. Environ. Contam. Toxicol. 1996, 57, 34–40.
  40. Mores, S.; de Souza Vandenberghe, L.P.; Júnior, A.I.M.; de Carvalho, J.C.; de Mello, A.F.M.; Pandey, A.; Soccol, C.R. Citric acid bioproduction and downstream processing: Status, opportunities, and challenges. Bioresour. Technol. 2020, 320, 124426.
  41. Berovic, M.; Legisa, M. Citric acid production. Biotechnol. Annu. Rev. 2007, 13, 303–343.
  42. Salihu, R.; AbdRazak, S.I.; Zawawi, N.A.; Kadir, M.R.A.; Ismail, N.I.; Jusoh, N.; Mohamad, M.R.; Nayan, N.H.M. Citric acid: A green cross-linker of biomaterials for biomedical applications. Eur. Polym. J. 2021, 146, 12.
  43. Wang, M.; Guo, Y.; Xue, Y.; Niu, W.; Chen, M.; Ma, P.X.; Lei, B. Engineering multifunctional bioactive citric acid-based nanovectors for intrinsical targeted tumor imaging and specific siRNA gene delivery in vitro/in vivo. Biomaterials 2019, 199, 10–21.
  44. Yang, C.Q. Effect of pH on nonformaldehyde durable press finishing of cotton fabric: FT-IR spectroscopy study: Part I: Ester crosslinking. Text. Res. J. 1993, 63, 420–430.
  45. Yang, C.Q. Effect of pH on nonformaldehyde durable press finishing of cotton fabric: FT-IR spectroscopy study: Part II: Formation of the anhydride intermediate. Text. Res. J. 1993, 63, 706–711.
  46. Yang, Y.; Li, S. Silk fabric non-formaldehyde crease-resistant finishing using citric acid. J. Text. Inst. 1993, 84, 638–644.
  47. Mohsin, M.; Ramzan, N.; Ahmad, S.W.; Afzal, A.; Qutab, H.G.; Mehmood, A. Development of Environment Friendly Bio Cross-Linker Finishing of Silk Fabric. J. Nat. Fibers 2015, 12, 276–282.
  48. Khan, M.M.R.; Tsukada, M.; Gotoh, Y.; Morikawa, H.; Freddi, G.; Shiozaki, H. Physical properties and dyeability of silk fibers degummed with citric acid. Bioresour. Technol. 2010, 101, 8439–8445.
  49. Chen, Z.J.; White, M.; Qiu, Z.C. Investigation of Vacuum and Steam Treatments to Heat Treat and Sanitize Firewood-Grade Ash Logs and Ash Firewood. For. Prod. J. 2017, 67, 258–265.
  50. Chu, Q.L.; Song, K.; Bu, Q.; Hu, J.G.; Li, F.Q.; Wang, J.; Chen, X.Y.; Shi, A.P. Two-stage pretreatment with alkaline sulphonation and steam treatment of Eucalyptus woody biomass to enhance its enzymatic digestibility for bioethanol production. Energy Conv. Manag. 2018, 175, 236–245.
  51. Lawther, J.M.; Sun, R.C.; Banks, W.B. Effect of steam treatment on the chemical composition of wheat straw. Holzforschung 1996, 50, 365–371.
  52. Fang, L.; Sun, F.Y.; Liu, Q.B.; Chen, W.C.; Zhou, H.; Su, C.Z.; Fang, K.J. A cleaner production process for high performance cotton fabrics. J. Clean. Prod. 2021, 317, 9.
  53. Rekaby, M.; Salem, A.A.; Nassar, S.H. Eco-friendly printing of natural fabrics using natural dyes from alkanet and rhubarb. J. Text. Inst. 2009, 100, 486–495.
  54. Li, R.M.; Wang, L.L.; Hao, B.R.; Wu, M.H.; Wang, W. New thickener based on s-triazine di-sulfanilic xanthan for reactive printing of silk fabric with double-sided patterns. Text. Res. J. 2019, 89, 2209–2218.
  55. Murate, H.; Terasaki, F.; Shigematsu, M.; Tanahashi, M. Improvement in the stretching property of paper yarn by shape memorization produced with high-pressure steam treatment. Sen-I Gakkaishi 2008, 64, 74–78.
  56. Cai, Z.S.; Jiang, G.C.; Yang, S.J. Chemical finishing of silk fabric. Color. Technol. 2001, 117, 161–165.
  57. Wang, R.; Zhu, Y.F.; Shi, Z.; Jiang, W.B.; Liu, X.D.; Ni, Q.Q. Degumming of raw silk via steam treatment. J. Clean. Prod. 2018, 203, 492–497.
  58. Wang, X.Q.; Kluge, J.A.; Leisk, G.G.; Kaplan, D.L. Sonication-induced gelation of silk fibroin for cell encapsulation. Biomaterials 2008, 29, 1054–1064.
  59. Stathopulos, P.B.; Scholz, G.A.; Hwang, Y.M.; Rumfeldt, J.A.; Lepock, J.R.; Meiering, E.M. Sonication of proteins causes formation of aggregates that resemble amyloid. Protein Sci. 2004, 13, 3017–3027.
  60. Grinstaff, M.W.; Suslick, K.S. Air-filled proteinaceous microbubbles: Synthesis of an echo-contrast agent. Proc. Natl. Acad. Sci. USA 1991, 88, 7708–7710.
  61. Gonzalez, V.; Wood, R.; Lee, J.; Taylor, S.; Bussemaker, M.J. Ultrasound-enhanced hair dye application for natural dyeing formulations. Ultrason. Sonochem. 2019, 52, 294–304.
  62. McNeil, S.; McCall, R. Ultrasound for wool dyeing and finishing. Ultrason. Sonochem. 2011, 18, 401–406.
  63. Velmurugan, P.; Shim, J.; Seo, S.K.; Oh, B.T. Extraction of natural dye from coreopsis tinctoria flower petals for leather dyeing—An eco-friendly approach. Fibers Polym. 2016, 17, 1875–1883.
  64. Peila, R.; Grande, G.A.; Giansetti, M.; Rehman, S.; Sicardi, S.; Rovero, G. Washing off intensification of cotton and wool fabrics by ultrasounds. Ultrason. Sonochem. 2015, 23, 324–332.
  65. Bahtiyari, M.I.; Duran, K. A study on the usability of ultrasound in scouring of raw wool. J. Clean. Prod. 2013, 41, 283–290.
  66. Kadam, V.V.; Goud, V.; Shakyawar, D. Ultrasound scouring of wool and its effects on fiber quality. Indian J. Fibre Text. Res. 2013, 38, 410–414.
  67. Mahmoodi, N.M.; Arami, M.; Mazaheri, F.; Rahimi, S. Degradation of sericin (degumming) of Persian silk by ultrasound and enzymes as a cleaner and environmentally friendly process. J. Clean. Prod. 2010, 18, 146–151.
  68. Wang, W.C.; Pan, Y.; Gong, K.; Zhou, Q.; Zhang, T.H.; Li, Q. A comparative study of ultrasonic degumming of silk sericin using citric acid, sodium carbonate and papain. Color. Technol. 2019, 135, 195–201.
  69. Devaraju, S.; Selvakumar, N. Effect of Ozone Treatment on the Dyeing Properties of Mulberry and Tassar Silk Fabrics. J. Eng. Fibers Fabr. 2012, 7, 21–27.
  70. Sargunamani, D.; Selvakumar, N. Comparative analysis of the effect of ozone treatment on the properties of mulberry and tassar silk fabrics. J. Text. Inst. 2011, 102, 870–874.
  71. Sargunamani, D.; Selvakumar, N. Effects of ozone treatment on the properties of raw and degummed tassar silk fabrics. J. Appl. Polym. Sci. 2007, 104, 147–155.
  72. Sargunamani, D.; Selvakumar, N. A study on the effects of ozone treatment on the properties of raw and degummed mulberry silk fabrics. Polym. Degrad. Stabil. 2006, 91, 2644–2653.
  73. Mahmoodi, N.M.; Moghimi, F.; Arami, M.; Mazaheri, F. Silk Degumming Using Microwave Irradiation as an Environmentally Friendly Surface Modification Method. Fibers Polym. 2010, 11, 234–240.
  74. Wang, F.; Zhang, Y.Q. Effects of alkyl polyglycoside (APG) on Bombyx mori silk degumming and the mechanical properties of silk fibroin fibre. Mater. Sci. Eng. C Mater. 2017, 74, 152–158.
  75. Bucciarelli, A.; Greco, G.; Corridori, I.; Pugno, N.M.; Motta, A. A Design of Experiment Rational Optimization of the Degumming Process and Its Impact on the Silk Fibroin Properties. ACS Biomater. Sci. Eng. 2021, 7, 1374–1393.
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